1. Technical Field
The invention relates to lift axles for load carrying utility vehicles and more particularly to a control system for such lift axles integrated with a comprehensive vehicle control system and providing substantial automation of the process.
2. Description of the Problem
Many utility vehicles are equipped with lift axles which may be raised under low load conditions to reduce vehicle rolling resistance and lowered to bring additional load bearing wheels into contact with a road under high load conditions to reduce per axle loading to within legal maximums. Obviously, a decision is required as to the appropriate times to raise and lower such a lift axle. The increasing sophistication of vehicle control systems has made much data available that might be used to indicate appropriate times for repositioning the lift axle. Issues relating to isolating this data and correlating the various sources of data for cooperative use have not previously been thoroughly addressed to the best knowledge of the present inventors.
Among the factors of interest in deciding whether to raise and lower and axle is the total vehicle load. This data can be isolated from air suspension pressure readings. Vehicle stability will be affected by changes in axle position, and thus an axle should not be repositioned if the vehicle is moving at more than a minimal rate of speed.